The present invention relates to a split torque gearbox, and more particularly to a rotary wing aircraft gearbox system.
A gearbox system of a rotorcraft or propeller-driven aircraft transfers power from a turbine engine to the rotor or propeller of the rotorcraft or aircraft. A typical system may direct power from several turbine engines to a single rotor or propeller. Since the rotational velocity of the rotor or propeller is significantly lower than the rotational velocity of the turbine engines, the turbine engine rotational velocity must be reduced by the gearbox system. In reducing the rotational velocity of the turbine engine output, torque is increased through a series of intermediate gear stages and shafts, before the final output drive is provided to the rotor. Relatively large gears are required near the final output drive to handle the high torque supplied to the rotors.
One prior art system includes a number of gears arranged for providing split-torque paths. The torque normally carried by a single drive train path is carried by two drive train paths to thereby split the torque of the original drive train path. The combined weight of these two split-torque paths is significantly less than the weight of the original single drive train path. While this prior art split torque system has managed to increase the horsepower-to-weight ratio in some situations, especially where total horsepower involved is substantial and where multiple input drive paths from different engines are present, this conventional approach still requires a relatively large weight and a relatively large volume.
Moreover, many conventional and split-torque gearbox systems are somewhat heavy and voluminous due to unequal load sharing. Unequal load sharing typically results when the transmission may not consistently split the load. This requires each gear to be sized to a dimension larger than optimal so as to assure adequate load capability even when the load is not consistently split. Furthermore, typical gearbox systems provide a single load path in which significant damage to a single gear may result in the disablement of the entire system.
Accordingly, it is desirable to provide a split torque gearbox system that is relatively uncomplicated and inexpensive to manufacture, has a reduced weight, and packaging size, assures an even split of loads, and generates independent redundant load paths.